Synthesis of vanillic acid using whole cell nitrilase of wild and mutant Gordonia terrae

Abstract

The resting cells of Gordonia terrae mutant E9 having enhanced nitrilase activity were used for biotransformation of 4-hydroxy-3-methoxybenzonitrile into vanillic acid. The maximum conversion was observed in 0.1 M phosphate buffer (pH 8.0), using 60 mM substrate and 0.75 mg_DCW resting cells in 1 mL reaction at 40 °C. K _m of the whole cell nitrilase of wild and mutant strains of G. terrae for this substrate were 20 and 16.6 mM, and V _max were 0.19 and 0.95 ${\text{Umg}}_{{_{\text{DCW}} }}^{{^{ - 1} }}$, respectively. Fed batch reaction for transformation of 4-hydroxy-3-methoxybenzonitrile using whole cell nitrilase of wild G. terrae resulted in 2.36 g of vanillic acid in 5 h with a catalytic and volumetric productivity of 0.78 ${\text{gg}}_{\text{DCW}}^{ - 1} {\text{h}}^{ - 1}$ and 4.72 gL⁻¹h⁻¹, respectively. The whole cell nitrilase of G. terrae mutant E9 resulted in higher catalytic and volumetric productivity, i.e., 1.68 ${\text{gg}}_{\text{DCW}}^{ - 1} {\text{h}}^{ - 1}$ and 10 gL⁻¹h⁻¹. A total 5.04 g of vanillic acid with 99 % purity were accumulated in 100 mL of reaction after 5 h.